The speech, on the footsteps of the historic Snowden House, heaped praise upon Iowans and served bread-and-butter conservatism.

"This is where my Iowa roots were firmly planted. And it's these Iowa roots and this faith in God that guide me today," she said.

In her speech, Bachmann cast herself as the best candidate to unite Republicans and take on President Obama in 2012. She said she would unite fiscal conservatives, social conservatives and Tea Party conservatives; Bachmann said she considered herself each of those types.

She dismissed the notion that she was pursuing the Republican nomination out of self-interest, a day after she faced a controversial question about whether she is a "flake."

"Now I seek the presidency — not for vanity, but because America is at a crucial moment," she said.

The speech was heavy on down-home themes for Iowa's voters, a clear signal that Bachmann will make an aggressive play in the state that hosts the first nominating contest of the 2012 cycle. Her prepared remarks mentioned "Iowa" 12 times, and she strayed significantly from those prepared remarks to insert more references to the state and town in which she was raised through the sixth grade.

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The speech was clearly intended to capture momentum suggested by a poll showing the three-term congresswoman was a front-running candidate in Iowa's caucuses next year. Twenty-two percent of likely Republican caucus-goers named Bachmann as their top choice in a nominee in the first edition of the Iowa Poll, published Sunday in The Des Moines Register. That puts her only one point behind former Massachusetts Gov. Mitt Romney (R), who's not likely to compete aggressively in Iowa, and ahead of a number of candidates who have put more effort into courting the state's voters.

Her entry into the race comes after months of public flirtation with running; she announced her candidacy at a New Hampshire presidential debate earlier this month, thereby stealing some of the spotlight from other debate participants.

The Obama campaign reacted to Bachmann's announcement by labeling her a candidate that "would erode the path to prosperity for middle class families."

"She voted for a budget plan that would extend tax cuts for the richest Americans on the backs of seniors and the middle class while ending Medicare as we know it," said campaign spokesman Ben LaBolt. "Congresswoman Bachmann introduced legislation to repeal Wall Street oversight – risking a repeat of the financial crisis -- and while she voted to preserve subsidies for oil and gas companies she opposes making the investments necessary to enhance America’s competitiveness and create the jobs of the future.”

Bachmann's strategy now will likely focus on building off her base of Tea Party supporters, whom she's assiduously courted over the past year, in part by founding the Congressional Tea Party Caucus. But she faces a challenge in expanding support beyond her niche of conservative activists, and gaining broader appeal among mainstream Republican voters.

The Tea Party is not a "fringe" movement, Bachmann said in casting herself as a firmly mainstream Republican.

"I am here in Waterloo, Iowa to announce today: We can win in 2012 and we will. Our voice has been growing louder and stronger. And it is made up of Americans from all walks of life like a three-legged stool," she said. "It's the peace through strength Republicans, and I'm one of them, it's fiscal conservatives, and I'm one of them, and it's social conservatives, and I'm one of them. It's the Tea Party movement and I'm one of them."

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Her campaign also clearly will make a play for Iowa's numerous social conservative voters. Bachmann made frequent reference to faith and religion — she is an evangelical Christian — during the roughly half-hour speech. She quoted scripture toward the end of her announcement speech, and attributed her decision to run to thanks for blessings she had received "both from God and from this great country."

Following her announcement, Bachmann will look to carry that momentum to New Hampshire and South Carolina, the two states that follow Iowa on the primary calendar, with events there in Tuesday and Wednesday, respectively.

But Bachmann's momentum could still be stymied by some of the late entries into the race. The popular assumption is that if former Alaska Gov. Sarah Palin (R) — who endorsed Bachmann for Congress last year — were to enter the race, the two would vie for the same voters. (Bachmann's said that Palin's decision whether to run wouldn't affect hers.) Other late contenders like Texas Gov. Rick Perry (R) also threaten to sap some momentum from Bachmann's candidacy, especially with Tea Party supporters.

Palin will be in Iowa on Tuesday to screen a new biographic movie, "The Undefeated" about herself.